1. Field of the Invention
The present invention relates to a photo film cassette. More particularly, the present invention relates to a photo film cassette of which a cassette shell is constituted of a plurality of shell parts joined together.
2. Description Related to the Prior Art
A 135 type photo film cassette is most widely used among other photo film cassettes, and consists of a cassette shell, a spool and photo film. The cassette shell has a metal tube and a pair of caps fitted on respective ends of the tube. A trailer of the photo film is retained on the spool, and contained in the cassette shell rotatably with the spool. When a photographer uses up the photo film after photography, he deposits the cassette to a photofinisher. In a photo laboratory, the entirety of the photo film is taken out of the cassette shell, cut off from the spool in a position exterior to a photo film passage port of the cassette, and subjected to processing for development and printing of photographs. After the photo film is developed, the photo film is cut off at a regular shorter length, inserted into photo film sheaths, and returned to the photographer.
U.S. Pat. Nos. 4,634,306 and 4,832,275 suggest a leader-advancing photo film cassette, in which a leader of the photo film is entirely pre-contained in a cassette shell, and when a spool is rotated, responsively the leader is advanced to the outside of the cassette shell. It has been proposed, as in U.S. Pat. No. 5,265,819 (corresponding to JP-A 4-362939), to construct such a cassette shell by use of a pair of molded shell halves, which are joined together fixedly in clicked fashion, so joined as to form a passage port like a slot for the photo film between the shell halves. Beside the passage port, a juncture of joining the shell halves is provided with a stepped structure, constituted of a groove in a first shell half and a ridge formed on a second shell half for being fitted in the groove. This stepped structure is formed to extend in a lengthwise direction of the photo film.
The developed photo film, as cut off and inserted into photo film sheaths, has an inconvenience in preservation, as the photo film cannot be folded in a still shorter size. A preserving cassette for a developed photo film is suggested in a commonly assigned co-pending patent application U.S. Ser. No. 07/910,914 (corresponding to JP-A 5-19441), for containing the developed photo film in roll form without being cut down into pieces. A preserving cassette has a cassette shell, a spool, an openable port lid for closing a passage port, and a leader-advancing structure for advancing the leader in response to rotation of the spool. The openable port lid is opened at a spacing enough for passage of the leader, and allows the leader advancement during the rotation of the spool.
The use of the preserving cassette with the ordinary photo film cassette sometimes has tendency of raising the amount of labor in handling the cassettes in photo laboratories, because the different cassettes must be discerned in handling suitably for the status of the photo film to be contained. This requires a dual-purpose cassette constructed to be convenient for containing both the undeveloped photo film and the developed photo film.
It is suggested in a commonly assigned co-pending patent application U.S. Ser. No. 08/091,626 to facilitate retention of a trailer of photo film on a spool and facilitate removal of the trailer from the spool. It would be conceivable to use an automatic photo film removing/loading device proposed in the co-pending application, with great convenience, for removing such a dual-purpose cassette from, and loading it with, the photo film. This removing/loading device is provided with a trailer separator/inserter which has an arcuate shape, which is inserted through a passage port, by which the spool within a cassette shell is accessed, and effects removal and retention of the trailer.
However, movement of the trailer separator/inserter through the passage port requires high precision in control of the separator/inserter, because the passage port has such a small space. The removing/loading device of high precision is obliged to be manufactured at a high expense. The automation in moving the trailer through the passage port also has problem in that plush or light-trapping ribbons inside the passage port may be damaged by the trailer separator/inserter of the removing/loading device. The damaged plush may make it impossible to exit the leader through the passage port even when the spool is rotated.
The construction of the leader-advancing cassette by use of two molded shell halves has a problem in automation in handling of the cassette shell: handling of the separate two shell halves to be joined is complicated, and raises the cost and size of the removing/loading device. If the stepped structure, formed between the shell halves, located beside the passage port and constituted of the groove and the fittable ridge, cannot be utilized for facilitation in handling of the cassette shell. Should the stepped structure be fitted together for conveyance of the cassette shell before loading of the photo film, the shell halves must be separated for being loaded with the photo film. To disengage the stepped structure would be by no means practical, because it is firmly engaged and inappropriate for preliminary use.